1. Field of the Invention
The present invention relates generally to fluid oscillators and more particularly to a low frequency hydrofluidic oscillator.
2. Prior Art
Fluid oscillators utilizing fluidic amplifiers along with a piston housed in a fluid receiving chamber to provide output pulses or flows of fluid responsive to oscillation of the fluidic amplifier are known. For example, such a structure is shown in U.S. Pat. No. 3,124,999. Although the frequency of oscillation of the output signal can be changed such can only be accomplished by mechanically changing the length and mass of the piston or the spacing of the ports which are alternately covered and uncovered by movement of the piston.
Other types of fluidic amplifier driven oscillators are controlled by mechanically opening or closing feedback passageways connected to the control ports of the fluidic amplifier. Such devices are shown in U.S. Pat. No. 3,340,896.
Other types of structures are such as is shown in Re. 27,352 wherein tuned resonant devices such as tuned cavities control the frequency of the fluidic amplifier.
Other pneumatic oscillators known to Applicant are those as shown in U.S. Pat. No. 3,568,702 and U.S. Pat. No. 3,682,042. In U.S. Pat. No. 3,568,702, a pure fluidic oscillator is disclosed wherein the oscillator comprises three bistable fluid amplifiers with interconnecting R-C circuits and wherein the control signal pressure is applied to the oscillator through additional fluidic conditioning circuits which control the frequency range of the oscillator. In U.S. Pat. No. 3,682,042 a motor suitable for driving reciprocatory stirrers or the like is directly driven by a bistable fluidic amplifier, the frequency of which is controlled by blocking a vent at the end of movement of a piston.
Although each of the oscillators known to Applicant as above briefly described operate adequately for the purpose intended, none utilize a fluidic amplifier to drive a reciprocal valve to in turn provide an output fluid signal the frequency of which is adjustable and is in a low frequency range that is much lower than the natural frequency of the fluidic amplifier.